When are soundwalls warranted?

Soundwalls are necessary in locations adjacent to the highway where peak-hour noise levels are greater that 65 decibels. A soundwall will be proposed if it can reduce measured noise levels along the highway by 5 decibels.

To be effective, how high do soundwalls have to be?

Heights of walls are based upon their ability to lower the level of traffic noise. If a soundwall height is reduced to a point where it no longer achieves this measured noise reduction, it will no longer qualify for federal funding (and it will not be built). An effective soundwall normally blocks the line of sight from a 5-foot-tall receptor to the 11.5-foot truck exhaust stacks on the highway.

What if I don’t want a soundwall built?

A soundwall will not be built if more than 50% of the first-row property owners (adjacent to the project area) do not want it.

Do soundwalls block dust, dirt, and soot (particulate matter) produced by freeway traffic?

Barriers provide some limited protection from highway particulate matter as evidenced by concentrations often found at the base of the highway side of a soundwall. Soundwalls likely have minimal effect in stopping airborne soot and other aerosol particulate matter and vehicular emissions.

Can asphalt absorb sound?

Yes, rubberized asphalt has been reported to reduce noise levels by up to 3 decibels. However, rubberized asphalt requires special conditions to cure properly and can be placed only in select areas.

Will Caltrans provide double-paned windows and insulation for my residence?

Caltrans normally provides insulation for non-profit public institutions (schools, hospitals, etc.). Soundwalls and berms are the normal form of noise protection offered by Caltrans to residences. If, after the project is completed, noise levels are 75 decibels or greater, or the project causes an increase of 30 decibels or more, Caltrans will consider noise insulation of private property.